The inside back surface of the eye, which contains the retina, blood vessels, and neural tissue, is called the ocular fundus. Many systemic pathologies, as well as ocular pathologies, cause changes in the appearance of the ocular fundus. As a consequence, virtually all ophthalmic exams and most general physical exams include observation of the fundus. This observation is most often performed using a device called an ophthalmoscope, a hand-held device that provides the observer with a magnified direct view through the patient's pupil.
There are a number of factors that can limit the usefulness of an ophthalmoscope examination. For example, many ophthalmoscopes have rather poor optical resolution, limiting the detail that is visible by the ophthalmoscope. Additionally, the patient's eye is constantly moving which causes the scene through the ophthalmoscope to shift continuously, making it difficult to observe any fundus detail. Further, the ophthalmoscope is not capable of creating a permanent record of the exam (e.g., an image of the fundus).
In an attempt to overcome these difficulties, cameras for fundus imaging were developed. For example, a typical modern fundus camera collects digital color images of regions of the fundus. These cameras are expensive and difficult to operate from an operator's standpoint. For example, to collect an image of the fundus with a typical fundus camera, a number of steps are undertaken. The patient looks toward the camera at a target. The operator adjusts the camera to achieve an acceptable image. For example, the operator may adjust the brightness of the illumination and/or the alignment of the optical system with respect to the patient's pupil, etc. To perform these steps with a cooperative patient typically requires extensive practice and experience. Imaging patients who are unable to hold their gaze or their eyes or head steady, or to understand the instructions, is even more difficult. As a result, these cameras often take poor quality images which may not be useful to observe patient pathologies.
Accordingly, what is desired are ocular fundus imaging systems, devices, and methods that alleviate, overcome, or at least reduce, one or more of these problems.